4 GRAPHICAL : 
MPASS CONVERSION © 
OHART AND TABLES 


COMPILED BY. | 
Masor JOHN F. FAIRCHILD 


56TH Pioneer Inrantry, U. 8. Army 








D. VAN NOSTRAND COMPANY 
_ MILITARY AND NAVAL BOOKS : 


Park PLAcE NEW YORK 





oe 


Hq., Prov. Depot for Corps and Army Troops, : 
Camp Wadsworth, 6/13/18. 


\ 


To the Adjutant General of the Army, Washington, D. cu 
J Recommending approval. 


2. This chart appeals to me as an excellent piece of 
work for which Major Fairchild should receive “commenda 
tion. Its utility in visualizing, and comparing angles; 
according to the several systems is obvious, and I think 
of sufficient value to warrant approval. Major Fairchild) 
was an engineer before entry into Federal Service and ; 





has performed some engineering work for me with marked 
ability. : 
. GUY CARLETON, 
Brigadier General, 
Commanding. { 


.061 (Pub. Div.) 4 
A-G..0., hnly 29 1918. 


é ; 
To Major John F. Fairchild, Hq. 1st Corps Troops, re) 
Camp Wadsworth, 8S. C. : 


Your letter reference ‘‘ Publication of, Graphical 
Compass Conversion Chart”’ is approved. 


By order of the Secretary of War, iy 
F. W. LEWIS, 
Adjutant General. 






GRAPHICAL 
“COMPASS CONVERSION 


CHART AND TABLES 


~ 







Compiled by 


< Major John F. Fairchild 


56th Pioneer Infantry U.S. Army 





|.. D. VAN NOSTRAND COMPANY 
te MILITARY AND NAVAL BOOKS 
| 25 Park Place NEW YORK | 


iL CAO TIO 






GRAPHICAL 
COMPASS CONVERSION CHARTS TABLES 


COMPILED BY 


MAJOR JOHN F. FAIRCHILD 
56TH. PIONEER INFANTRY U.S.ARMY. 


SERG'T CLARENCE R.HAYWARD. ORAFTING ASSISTANTS. SERG'T ROBERT C.SCHOPP 
54TH PIONEER INF, U.S.A. 5IST. PIONEER INF. U.S.A. 


10° 
60-0" yun 


° 


\ 
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—— ce cee 


COMPASS TABLES FRENCH COMPASS SYNONYMS 
ROM ARIOUS AUTHORITIES 


For the 
SEXAGESIMAL (English); CENTESIMAL (French) and MILS(Military) SYSTEMS. | Grade; Grad; Degree; 6;%3;%. 
[Degrees [Minutes [Seconds] | Grades [Centigrades[pectwiigraded | Mils  |wincte Contectrule a 
ac = 1r 


Seay ee + Minute Centesimal; Minute *;°¢. 
= 60” * | Deci-Miligrade; Seconde; 
Seconde —Centesimal; “;¢, 


VARIOUS MILS SYSTEMS 

True’ Tan='/,000=6,283,18 to Circle. =3726.265'— 636.624 

Common= 1600 System-6400 to Circle.=3’22.57=6*°25> 

Quadrant = 90 Degrees = 100 Grades = 1,600 Mils Rimailho”System,=6,000 to Circle.=3’367=6°6.667" 
Circle =360 » =400 » =6400 » German Heavy Artillery=5760 to Circle=345"=6'94.44.4" 

Copyright, 1918, by D. VAN Nostrand Company 








GRAPHICAL COMPASS CONVERSION CHART AND _ 


TABLES 


et 


The graphical chart is designed, primarily, to afford a ready method of 


comparison between the American (English) and French method of denot- 
ing circle and magnetic compass angles and also of comparison with the 
| mils system used in military practice, accompanied by a clock face fdr 
| assistance in visualizing angles. 


. It consists of a Mariner’s Compass (la ma‘ine boussouie), showing the 
| twelve principal compass points, and the mariner’s designation of each 
| point with their abbreviation and quadrant direction in both English and 
| French. 


: Outside of the Mariner’s Compass is given a, circle divided for the 6400 
| divisions of the “common” mils system. 


Outside of the mils circle is given a clock face for assistance in visual- 


| izing angles. 
| outside give the minutes. 


The inside divisions and numbers give the hours and those 
A clock hand in passing from 12 o’clock to. 


1 o’clock passes through an angle of 30 degrees or 333 grades; from 12 to. 
| 2 o'clock of 60 degrees or 663 grades; from 12 to 8 o’clock of 90 degrees or 


} 100 grades and 30 on around the clock face. 
| Tepresents an angle of 6 degrees or 63 grades. 


Each minute on she clock | 


4 


Next to the clock face is given a circle divided according to the French | 


Centesimal or “grade” system. The inside figures state the divisions 





trom 0-400 grades around he circle, clockwise, while the outside figures | 


| state the divisions by quadrants from the north and south. 





(English) used in America. The inside figures state the divisions from | 
| 0-360 degrees around the circle, clockwise, while the outside figures state 
| the divisions by quadrants from the north and south. 2 


Outside of the circles are given the English and French Gesznat ony of | 


| the four quadrants. 


The “‘ Compass Tables ”’ 


~ 


on the face of the chart give on the left of the 


upper space the English system complete in itself and in the center of the | 


| second space the French system complete in itself. 


Opposite each of these ‘ 


| is given the value of the subdivision in terms of the other system and also 





















































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The outside circle is divided according to the Sexagesimal system | i 


1 on the face of the chart. 


of the “ common ”? mils system. Below is given the value of a mil in each 


| of the other systems and the division of the quadrant and si ii ee each of 


the three systems. 


"The research necessary to obtain accurate information in the prepara- 


tion of the chart developed the fact that various French and English tech- 


nical and military dictionaries and works use different terms in referring 
to%he French circle divisions. A table of all such synonyms found is given 
In the chart and tables those terms are used 
which seemed the most harmonious and euphonious and which afforded 
no chance for confusion with those used in the other tables. - 


The research also developed four “ mils” systems in use. The original 


or “ true ” mils system was devised for military use, so as to give an angle 
based on a direct relation between the tangent of the angle and the radius 


of the circle (the range of the artillery) this relation being 


1 =tangent 
1000 = radius of circle. 
> 
This scheme divided the circle into 6283.18 parts, each part being called a 
“mil.” This odd division was found cumbersome and about 1880 Colonel 
Rimailho, a French officer, devised the system (“‘Rimailho”’) of using an 
even 6000 parts to the circle instead of 6283.18, making an error of 283.18 
parts from the “true” system. 


This amount of error was found unsatisfactory and the “common” mils 
system of 6400 divisions to the circle was adopted, this number being the 
nearest even hundred to the “true” system, making an error of only 116.82 
points instead of 283.18 as in the ‘‘Rimailho” system. 







A table of these four m il systems is given on the face of the chart. 


a The chart can be used as a protractor by cutting out a small triangle 
at the 180 degrees—O degrees or 90 degrees—90 degrees points and half of 
the small circle in the center of the mariner’s compass and using a ruler to 


| carry the angle over the chart paper. 








s 
The general Conversion Tables accompanying the chart will enable the | 
use in computation of any table of logarithms or natural functions by con- 
verting the given angle into the angular designation on which is based the 
available table of logarithms or natural functions. 





























































































































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CONVERSION TABLE COMMON MILS SYSTEM TO SEXA 
-  GESIMAL AND CENTESIMAL SYSTEMS 


Mits TO DEGREES, ETC., AND GRADES, ETC. _ 


























SMe Deniees Minutes Seconds Grades ares Rete : 
1 0 3 22.5 0 6 25 
2 0 6 45 0 12 Be 8 
3 0 10 07.5 0 18 ee 
4 0 13 30 0 25 0. a 
5 0 16 52.5 0 31 25 = 
6 0 20 15 0 37 50° 4 
7 0 23 87.5 0 43 75 4a 
8 0 27 0 0 50 oO. § 
9 0 30 22.5 0 56 25 
. 10 0 33 45 0 62 50 
20 1 07 30 1 25 0s 
30 it 41 15 1 87 50 4 
40 2 15 0 2 50 Oia 
50 2 48 45 3 12 50 
60 3 22 30 3 75 Ogg 
70 3 56 15 4 37 50 
80 4 30 0 5 0 On 
90 5 03 45 5 62 50x 
100 5 37 30 25 0 a 
200 11 15 0 50 oy 
300 | 16 52 30 75 0 4 
400 | 22 30 0 0 0: 
500 | 28 07 30 25 0-4 
600 | 33 45 0 | 50 0 j 
700 39 22 30 75 0 
800 45 0 0 0 0. 
900 | 50 37 30 25 0-4 
1000 | 56 15 0 50 b.% 4 
1100 | 61 52 30 75 0°. 
1200 | 67 30 0 0 O% 
1300 | 73 07 30 25 0-2 | 
1400 | 78 45 0 50 ox 7 
1500 84 22 30 75 0 
1600 | 90 0 0 0 08g 





To reduce other mils systems to ‘‘Common”’ mils, multiply ‘‘ True’’ mils by 1. 018592; 1 
multiply ‘‘Rimailho” mils by 1.066667; multiply German H. A. mils by 1.111111. 






















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